Surface modified ZrO₂ and TiO₂ nanoparticles embedded in organic photopolymers for highly effective and UV-stable volume holograms

The improved synthesis of large quantities of small (hydrodynamic diameter 6–8 nm) TiO₂ and ZrO₂ nanoparticles tailored as a high refractive index agent in holographic acrylate photopolymer composites has been developed. The surface of the particles was modified by p-dodecylbenzenesulfonic acid (organic shell weight fraction is about 50–70%) to render them highly compatible with organic monomer mixtures avoiding aggregation. The exposure to the interference pattern provides fast one-step formation of permanent highly efficient volume phase gratings with excellent transparency in the visible range. A high refractive index modulation amplitude n₁ of about 0.0165 has been achieved in the composites containing 25 wt% of TiO₂ nanoparticles. The level of light scattering in the gratings does not exceed 8–10% compared to the film without nanoparticles. The holographic grating based on acrylates doped with ZrO₂ nanoparticles, first employed in this work, exhibited high photostability in contrast to holographic nanocomposites with TiO₂ nanoparticles. Possible applications of such photocurable organic–inorganic nanocomposites are holographic diffractive elements for a number of optical and electro-optical applications or devices based on ordered arrays of functional nanoparticles within organic films.